Electrical protective system



May 23, 1950 F. E. SPAULDING, JR

ELECTRICAL PROTECTIVE SYSTEM Filed sept. 1o, 1947 Patented May 23,1950

ELECTRICAL PROTECTIVE SYSTEM Frank E. Spaulding, Jr., White Plains, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application September 10, 1947, Serial No. 773,170

12 Claims. 1

This invention relates to a protective arrangement for an electron discharge device signalling system.

An object of the present invention is to prevent damage to electron discharge device equipment in a signalling system in the event of arc or flash-over or internal breakdown of the high voltage components.

Another object is to enable the use of an undercurrent relayas a protective device in a high frequency generating system, for preventing damage to the vacuum tubes in the event output current falls below a predetermined value.

A further object is to provide a protective arrangement for an electron discharge device high frequency system in which the system may be controlled or restored to an operating condition from a location which is removed from the electron discharge device apparatus.

A more specific object is to provide an undercurrent relay protective arrangement in a pulse type object locating or radar transmitting system, for disconnecting the high voltage power supply from the main power supply in the event of a reduction in output from the system below a predetermined value. y

A detailed description of the invention follows in conjunction with a drawing whose single figure illustrates the protective arrangement of the invention applied to the output stages of an electron discharge device object locating system.

Referring to the drawing, there is shown the pulse modulator or keying tube of the transmitter of an object locating system. The anode of this tube |00 supplies pulses of negative polarity through a coupling condenser to the cathode of a magnetron |I0. The magnetron is shown diagrammatically as a tube having a cathode connected to the coupling condenser, an anode connected to ground, and a coupling loop for supplying radio frequency output energy to a suitable antenna via a connection 80, such as a wave guide. In practice, the anode of the magnetron may be a cavity resonator in whose interior the output loop is located.

For supplying high voltage to the anode of the pulsing tube stage |00, there is provided a 15,000 volt power supply 200 whose output is connected to the anode load resistor |50 for the stage |00.

The 15,000 volt power supply 200 includes a pair of rectiers M and N and a pair of transformers T and TI. The cathode of rectifier M is connected to one terminal of a bleeder resistor P while the anode of rectifier N is connected to the other terminal Aci? bleeder resistor P. The

2 midpoint of resistor P is connected to one terminal of the secondary winding of transformer T. The filaments of the rectiers are heated from current supplied by transformer Tl. This is a conventional voltage doubler type of rectifier circuit.

One terminal of the primary winding of transformer T is connected through a rheostat I6, lead I1, onevside of on-off double-pole switch S and lead 3| to the common bus 2.Y The other termina1 of the primary winding of transformer T is connected to lead i4 and armature A of an undercurrent relay l0. The contact B of this relay is adapted to engage the armature A and is connected through lead |3, the left side of ori-off switch S and lead 30 to the operate bus 4. It will thus be seen that the circuit through the primary winding of transformer T is controlled by the condition of the undercurrent relay.

Four buses 2, 3 and 4 within a cable extend from the electron discharge device apparatus shown in the drawing to a remote location at which there is positioned the main power switch 50 and the cathode ray tube, not shown. .This main power switch has three contacts identified as off, standby and operate, and a rotary armature adapted to engage any one of these contacts at the will of the operator.

The protective arrangement of the invention includes the undercurrent relay l0, one termina1 of which is connected to ground through a meter A and the other terminal of which is connected through a damping choke i6 and a damping refsistor '|5 to thecathode of the magnetron. vIn circuit with this last terminal of undercurrent relay l0 is a radio frequency bypass condenser 36 and a time-lag or holdover condenser 35.

Another relay |5 is provided whose operating winding is connected to the power supply side of the on-off switch, as shown, via leads 25 and 25. This relay has two sets of contacts viz: C,A D and E, F. Contact D is connected to the upper terminal of undercurrent relay I0 while contact or armature C is connected to the bus to which is supplied 24 volts D. C. auxiliary operating supply for undercurrent relay l0. Contact F is con,- nected through lead l to the lament transformer for the magnetron, and also through resistor R to the standby bus 3 to which 115 volts-60 vcycle alternating current is connected on some positions of the remote main power switch 50. should be noted that contacts E' and F short circuit or shunt out resistor F in the non-operated position of the relay I5. The lament transformer for1 the magnetron is also connected Itv attendants controlV point at which the cathode ray tube is found is in the oif position-,Nall power is removed from the four buses I, 2, 3 and 2,508,648 L. L i: .c

4. When this switch 50 is on the tfstand-by position, a motor generator, not shown, will bestarted up to produce the 115 volts--60 cycles A. C. which is supplied between buses 2 and 3.V4 This applies when the power source is 115 or 230 volts D. C. When the object location system to which the 'invention is applied is employed on a ship having :53,: volts-60 cycles alternating current supply howevensuch a motor.v generator Yneed not be used, and an A. C.l contactor, not shown, connects the-.115 volt supply to buses 2 and 3. In this conditionofLswitch 50, when its armature is on the to maintain relay I0 operated. The normal operation of the magnetron I I0 causes a current to flow through damping resistor 'I5 and damping choke 'I6 and the winding of relay I0 to maintain this relay operative. Because of the rapidity of the pulses produced by the pulse modulator (750 or 3,000 per second in accordance with the design fof a radar system actually tried out in practice), the undercurrentrelay I0 will not fall back in the extremely shortY time intervals between pulses. The polarity of the pulses appearing on the cathode ofthe magnetron are negative relativeto the ground.

Theoperation of'relay I5.in the operate position of the `inainfpower switch 50 also opens contactsE'andLF, this action introducing the resistor Rlin the filament heating circuit of the magnetron. `This resistor enables the magnetron to standby contact, and assumingV the` ori-off v switch YS to be closed, the system is conditioned for heating all laments'of the different vacuum tubes; also the 24 volt D. C. auxiliary control supply-is energized. Thus, the filaments ofthe rectiers M and :Nare heated Vvia leads 5 and 6 which are Vconnected to standby bus 3 and common bus '2,.and1the magnetron filament is heated via leads `Izand v8.- In this .position of the switch 50, the resistor VRis shortcircuited by virtue of the closed contacts E and F of relay I5 now unenergized. Current .is supplied fromthe 24 volts D. C. auxiliary supply bus l, 'over a circuit yincluding contactsCand D, to operate undercurrent relay I0. The operation of. relay I0 closes `contacts A and Bfandcompletes a lcircuitto the primary vwinding `of' the-15,000volt power supply unit `200,v over an obvious path Ywhichincludes the operate bus 4, the'left 'side of switch S, lead I3, contacts B and A."of;;relay I0, lead I4, the primary winding of transformer T, rheostat I6, lead I1, the right side of "switch S, to the common bus 2. The 15,000 volt power supplyfunit 200.` is now ready to function whenthe power switch Eilfs turned to the' "operate position. The standby position ofthe 'main power switch 50 enables the avoidance of `"excessive-wear and tear on expensive tubes if the.

transmitter is to be left unattended for short iperiods. It also-keeps the equipment ready for instantuse after the initial three minute wait eb'us is connected to theopera'te,bus 4 through 'the armature andthe operate contact of switch 50,- as a result of which current is supplied to theprim'ary winding of transformer T, and 15,000 fv'oltsis supplied bythe unit 200 tothe anode load resistor I50 for the `pulse modulator I00. In this operate position of switch 50, relay vI5 will o perate vover an obvious circuit via leads 25 and 28 'and will open-contacts C, D and E, F. The openof contacts C, D will remove the 24 volts D.V C. `auxiliary'supply from the winding of relay I0, lliutithis relay I0 will remain operated'for a short time interval of the order of 1/zisecond because lofthe charge built up on capacity 35. During this time interval, the pulse modulator |00 will supply voltage `pulses of proper polarity and amplitude to operate `the magnetron I I0 and thereby function on its desired characteristics during pulse operation.

Erom. the foregoing, lar'nents ofthe different tubes :are preheated to operating levels before the system is actually set into operation. There is provided a three-minute time delay relay |25 in .the-operate bus A#I `circuit Y in order to prevent the applicationof volts alternating current. tothe Vbus-Land the 15,000 volt power supply circuit 200-be'fore the passage ofv three minutes, thus assuring .preheating of filaments orheaters to-their 1correctlevel before the system can.. be operated `afs a lpulsing transmitter. Itshould be noted that the winding-of Ythe time delay relay. -I25 'is vconnected across buses 2 and 3, while the contactsof this Yrelay are'serially arranged vin series with operatefbus 4.

Should the current inthe-magnetron be linterrupted for. more than` second --for any reason, theY undercurrent relay-I10 will fall back andopen the circuit through the primary-winding of transformer T Yin vthe 15,000vo'lt 'power supply unit 200. This` action will removefp'ower Afromthe anode load resistor 150. This action will prevent ldamage to the magnetron and l'pulse A'nfufa'dulator and the 15,000 volt power -supplyunit200/ which might Yotherwise occur. The .interruption of the `current in the magnetron circuit may beoaused by vac- 'uumtube arcing, failure Vof *any* lone ofthe rectiler tubes M'orN,y theabsence of suitable trigger pulses in the radarcircuitconnected to the pulse modulator AI 00 lor failure Vofiany ofthe high volt. agecomponents.

In order to restore-the system to the normal operating condition-afterany undesired interruptionof current in the` magnetron which causes-the undercurrent-relay Ato fall back, the main power switch-50 should be turned to the standby position, `andafterwards back to the operatev position. :The V'steps of" voperation have been Vdescribed above'for these two positions- Y An advantage Yof the 'present invention over and above the protection afforded vto the various elements .in the event the'magnetron current falls below a predetermined value is that all operatingcontrols may be locatedat Va point removed fromV the transmitter portion of the equipment.. Thus, the -vmain power Vsupplyswitch 50 canbe located at the radar operating positionfat vwhich the Vattendantimay `be stationed.

Althoughthe invention has been .particularly describedA with Vreference to a; radar or object location system, it should beunders'tood that 1it is not-limited to this-'type of 4a 'transmitter and JM that its application lin 'other electron vdischarge it. will be seenthat the i device systems will be evident to those skilled in; the art.

, What isclaimed is:

l.; In electron discharge transmitting apparatus, a final output stage, a driving stage coupled to said output stage, a high voltage power supply unit for said driving stage, said high voltage supply unit including a transformer having a primary winding adapted to be connected to a main power source, an undercurrent relay coupled to an electrode of said iinal outputfstage and responsive to the flow of normal operating current in said output stage, said relay having an armature and a make contact adapted to engage said armature when said relay is operated, said armature and contact being arranged in series relation to said primary winding and said main power source, whereby the reduction of current in said final output stage below a predetermined value causes said relay to fall back and said armature to disengage said Contact thereby disconnecting said main power source from said high voltage supply unit.

2. A protective arrangement for electron discharge device transmitting equipment, comprising a, nal output stage, a driving stage coupled to said output stage, a high voltage power supply unit for said driving stage, said high voltage supply unit including a transformer having a primary winding adapted to be connected to a main power source, an undercurrent relay coupled to an electrode of said final output stage and responsive to the flow of normal operating current in said output stage, said relay having a pair of cooperating contacts which are open when said relay is not operated, a connection from one terminal of said primary winding to one of said contacts, a connection from the other contact to said main power source, whereby said connections and contacts are arranged in series between said primary winding and said main power source, said relay requiring a predetermined minimum value of current therethrough from said final output stage to operatively connect said high voltage supply to said main power source.

3. In electron discharge transmitting apparatus, a iinal output stage, a driving stage coupled to said output stage, a high voltage power supply unit for said driving stage, said high voltage supply unit including a transformer having a primary winding adapted to be connected to a main power source, an undercurrent relay coupledto an electrode of said iinal output stage and responsive to the iiow of normal operating current in said output stage, said relay having an armature and a make contact adapted to engage said armature when said relay is operated, said armature and contact being arranged in series relation to said primary winding and said main power source, whereby the reduction of current in said nal output stage below a predetermined value causes said relay to fall back and said armature to disengage said contact thereby disconnecting said unit main power source from said high voltage supply, another relay having an operating winding coupled to said main power source, a pair of break contacts for said last relay, a resistor having one terminal connected to one of said break contacts and also to one side of the filament circuit for said nal output stage, connections between the other terminal of said last resistor and said other break contact Yand said main power source,

whereby said resistor is short-circuited by said break contacts in the unoperated conditions of said last relay, and a connection from thel other side oi saidlament circuit to said main power source, whereby said resistor is inserted into said filament circuit upon the operation of said last relay.

4. In a pulse type transmitter, apulse modulator tube, a magnetron having a cathode electrode kand an anode electrode, a connection be-o tween the output of said modulator tube and one of said electrodes of said magnetron, a connection between the other said electrode of said magnetron and a point of reference potential, a high voltage supply unit for said modulator tube, said high voltage supply unit including a rectifier and a transformer for feeding energy thereto, an undercurrent relay connected between said point of reference potential and the output connection from said modulator tube, said relay having a pair of makecontacts, a main source of power supply for said high voltage supply unit, and means for connecting the primary winding of said transformer and said pair of make contacts in series relation relative to said main source of supply, whereby the reduction of current in said magnetron below a predetermined value causes said undercurrent relay to fall back thereby opening said make contacts and disconnecting said main power source from said high voltage supply unit.

5. In a pulse type transmitter, a pulse modulator tube, a magnetron having a cathode electrode andV an electrode, a connection between the output of said modulator tube and one of said electrodes of said magnetron, a connection between the other said electrode of said magnetron and a point of reference potential, a high voltage supply unit for said modulator tube, said high voltage supply unit including a rectifier and al transformer for feeding energy thereto, an undercurrent relay having one terminal of its operating winding connected to a point of reference potential and the other terminal of its operating winding connected through an inductance coil and a resistor in series to the output connection from said modulator tube, a condenser connected between said last terminal of the relay winding and said point of reference potential, said relay having a pair of make contacts, a main source of power supply for said high voltage supply unit, and means for connecting the primary winding of said transformer and said pair of make contacts in series relation relative to said main source of supply, whereby the reduction of current in said magnetron below a predetermined value causes said undercurrent relay to fall back thereby opening said make contacts and disconnecting said main power source from said high voltage supply unit. f

6. In a radio transmitter, a vacuum tube radio frequency oscillation generator, a driving stage coupled by means of a connection to Said generator for supplying pulses thereto of such polarity and magnitude as to cause said generator to produce oscillations for a time interval not exceeding the duration of the applied pulse, a high voltage supply unit for said transmitter and including a rectifier and a transformer for feeding energy to said rectifier, an undercurrent relay having one terminal of its operating winding connected to a point of reference potential and the other terminal of its operating winding con` nected tosaid connection from said driving stage to said generator, a, holdover condenser con denser connected between said last terminal ofi said vrelay windingand said' point of-reference' potential, said-holdover condenser havingv such value that the charge built up thereonduring the application of pulses to' said'generatorfby said driving stage will hold said undercurrentrelay operated for a predetermined interval Yof time after the cessation of aY driving pulse, said relay having a pair of make contacts, a main source of power supply forsaid high voltage sup plyfunia'and means for connecting the primary windingof said transformer and said pair of make contacts in seriesf relation relative to saidv main source of supply, whereby the reduction of current in' said generator below a predetermined value Ycauses said undercurrent relay `to fall back thereby opening said make contacts and disconnecting said main power source from said high voltage'supply unit.

L In a pulse type transmitter', a vacuum tube radio frequency'oscillation generator, a driving stage coupled by means of a connection to said generator for supplying pulses thereto of such polarity and magnitude as to cause said gen-A erator to produce oscillations for a time interval not exceeding the duration of the applied pulse,-

Va high voltage supply unit for said transmitter and including a rectiiier and a transformer for. feeding energy to said rectifier, an undercurrent relay having one terminal of its operating winding connected to a point of reference potential and the other terminal of its operating winding Y Vwinding-of said transformer dacross-said opere connectedthrough an inductance coil and a re-v sistor Yin series to said connection from said driving stage to said generator, a holdover condenser connected between said last terminal of saidv relay winding and said point of reference poten-V tial, said holdover condenser having such value that the charge built up thereon during the application of pulses to said generator by said driving stagerwill hold said undercurrent relay operatedA for a predetermined interval of time after the cessation of a driving pulse,V said relay hav-V ing a pair Vor" make contacts, a main source lof Y power supply for said high voltage supply unit,

and means for connecting the primary winding of Vsaid transformer and said pair of make contacts in series relation relative to said main source of supply, whereby the reduction of current in said generator below a predetermined value causes said undercurrent relay to fall back Vthereby'opening said make contacts and disconnecting said main power source from said high voltage supply unit.

8. In a radio transmitter, a nal output strage,

, anda driving stage coupled to said output stage,

a high voltage power supply unit coupled to said driving stage, said unit including a rectifier and a transformer for supplying energy to said rec-Y tier, a main power switch havingan armature adapted to alternately Vengage any one of two contacts` which may be identiedas'an off contact, andan operate contact, a first busV connected `to the operate contact on said main power switch, a second bus connected to the armature on said -main power switch,'and a third bus, said second and third buses being connected toa source of low frequency alternating current voit-agaan undercurrent relay coupled toV an electrode of said final output stager and resp/0n-` sive tothe now of normal operating current inv said output stage, said relay having a pair of cooperating make contacts adapted to engagev eachl other in' the operated condition of said relay, and means for Vconnecting the primary Y tier, a main power switch Vhaving an armature adapted to engage any one of three contacts which may be identified as an off Contact, a' standby contact, and an-operate contact, a iirst bus connectedto the operate" contacten said main power switch, a'sec'ond bus connected to the armature on said main power switch, and a third bus, said second and third buses* being connected to a source oi low frequency alter-y hating current voltage, an undercurrent relay coupled to an electrode of said nal output'sta'ge and responsive to the flow of `normal operating current'in said output stage, said relayhaving a pair of cooperating make contacts adapted to engage each other in the operated condition 'of saidrelay, a leadv connecting one terminal of the primary windingofsaid transformer to one Vmake contact of said'lrelay, another lead connecting the other make contact of said relayto said operate bus, and a time delay device lo-k cated in series with said operate bus at a loca-V tion between said main power -switcli-and` the junction of said operate bus and said last lead.

10. In a radio transmitter, a nal output stage, and a driving stage coupled to said output stage, a high voltage power supply unit coupled tor said driving stage, said unitincluding a rectier and atransformer for supplying energy to said rectirler, a main power switch having an armature adapted to engagel any one o'irthree contacts which may beidentied as an"oi contact, a standby contact, and an operate contact, a first bus connected to the Voperate contact on said main power switch, a second bus connected to the armatureon said main power switch, and a third bus, said second and tloird`Y buses being connectedv to a source of low frequency alternating current voltage, an under-V current relay coupled to an electrode of saidV iinal output stage and responsiveto the now of normal operating current in usaid output stage;Y

sai-d relay'having a pair of cooperating make con-j tacts :adapted to engageeach otherv in the operated condition of said' relay-a leadconneoting one terminal of the primary winding of saidV transformer'tol one make contact of said relay, another-lead connecting the other makecontact Vof said relay to said operatebuaanda'time delay Y.device located inVV `series withV said oper-"- ate bus at a location between said main-power switch and the 'junction of said operate bus and said last lead,v and means for heating `the filaments of said rectifier and said final output Y stagel from said second andy thirdbuses'.

ll.Y In a pulse type transmitter, a vacuum tube Y radioV frequency oscillation generator, a driving 'voltage supply unit'rfor saidY transmitter and in@ cluding a rectifier `and a transformer for, feed-- ing energy to said reotier, anundercurrent relay having one terminal of its operating winding connected to a point of reference potential and the other terminal of its operating winding connected through an inductance coil and a, resistor in series to said connection from said driving stage to said generator, a holdover condenser connected between said last terminal of said relay winding and said point of reference potential and having such value as to maintain said relay operated for a predetermined interval of time after the cessation of driving current from said driving stage, said relay having a pair of make contacts, a main source of power supply for said high voltage supply unit, means for connecting the primary winding of said transformer and said pair of make contacts in series relation to said main source of supply through a time delay device, whereby the reduction of current through said generator below a predetermined value causes said undercurrent relay to fall back thereby opening said make contacts and disconnecting said main power source from said high voltage supply unit, and means including separate transformers for heating the filaments of said rectier and said generator from said main power source.

12. In electron discharge transmitting apparatus, a iinal output stage, a driving stage coupled to said output stage, a high voltage power supply unit for said driving stage, said high voltage supply unit including a transformer having a primary winding adapted to be connected to a main power source, an undercurrent relay coupled to an electrode of said final output stage and responsive to the flow of normal operating current in said output stage, said relay having an armature and a make contact adapted to engage said armature when said relay is operated, said armature and contact being arranged in series relation to said primary winding and said main power source, whereby the reduction of current in said nal output stage below a predetermined value causes said relay to fall back and said armature to disengage said contact thereby disconnecting said main power source from said high voltage supply unit, a second relay having an operating winding coupled to said main power source, a pair of break contacts for said last relay, a connection from one break contact of said last relay to that terminal of the operating winding of said rst relay which is connected to the final output stage and a connection from the other break contact of said second relay to a source of unidirectional potential of such magnitude as to enable the operation of said undercurrent relay, and a main power switch for controlling the operative association of said main power source with said high voltage supply unit.

FRANK E. SPAULDING, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,756,131 Ohl Apr. 29, 1930 1,756,132 Ohl Apr. 29, 1930 1,934,525 Davis Nov. 7, 1933 1,955,352 Wallace Apr. 17, 1934 1,975,812 Wallace Oct. 9, 1934 

